Whatever tips or rules you read about pruning your marijuana plants, the goal should be one: make your plants give you the biggest yield.
Among all the existing ways and methods of pruning, you need to choose only those that suit you best. The methods greatly depend on the growing technique you use. The lollipop technique requires a completely different way of pruning than the Sea of Green method. Basically, growers prune marijuana in order to either stimulate or minimize branching. So you need to decide in advance what exactly you want to get.
A huge marijuana plant does not necessarily mean a huge yield. The taller the plant grows, the more nutrients and water it uses. But the buds grow only on the ends of the branches, so even if your plant is as tall as a giraffe, you will still get buds on the very top of it (which you will not be able to reach without a portable ladder), just like the neighbor plants with average height.
Not only does it look bad, it may also cause problems like attracting the undesirable attention of passers-by and shadowing other plants. So you had better keep an eye on your garden and cut the top of this kind of plants on time.
Pinching the very top of the cannabis plant can not only prevent giraffe-like plants but also create a bushy kind of marijuana with more branches and, therefore, more buds. Once you remove the upper nods, the stem will split into two branches. You can pinch their tops as well to get four branches instead. Of course, those branches will be weaker than one strong stem, but as they are closer to roots, they will receive more water and nutrients, and if you give your plant a bit more time than usual, on every top of the new branches you will get nice resinous buds that altogether will make much more yield than if you had left the stem untouched.
Excessively bushy plants are good for growing outdoors, but growing those monsters indoors is a bad idea. The plant's energy is directed in too many ways, the inner branches do not get enough light and air and therefore provide very little (if any) yield.
A very dense structure of the plant creates conditions for powdery mildew and pests, and they can stay there unnoticed until it is too late and they contaminate the whole garden.
To optimize your garden's productivity, it is important to get rid of the branches than turn your marijuana plant into a Christmas tree. Look carefully which branches you want to save and which ones should be removed. It is better to save the strongest ones and to cut off those that are weak, overshadowed, and take too much space. Generally, the final size of your plant and the number of branches depend on the space you can provide for this particular plant; pruning all the plants according to the same scheme is not the best idea.
It is also not good to prune too many branches of the plant with no serious reason. Every time you cut off a branch, it causes stress for a plant that has to spend its energy on healing itself instead of sending this energy for growing or flowering. So prune wisely.
An open cut can make marijuana very vulnerable to pests and fungi. Some growers suggest using a tree wound sealer, though it is difficult to find the one that really cures the wound instead of just covering it. If you have noticed any sign of infestation, immediately remove the infested area with no pity. Sometimes, one single day is enough for fungi to spoil the whole plant, so you had better look out.
To minimize the danger of infestation, it is better not to let your plant bleed. In this case, a sharp knife will only make it worse. If the size of the branch allows it, it is better to pinch it off. In this case, you will not slice the branch but squeeze it, so the size of the wound will become smaller. If the branch is too thick, try to use wire cutters (the duller, the better).